What happened to the human mind after the Howiesons Poort?

Lombard, Marlize ; Parsons, Isabelle

Introduction

Recently, Laurel Phillipson and Marlize Lombard published evidence for Middle Stone Age bow and arrow technology in southern Africa (Lombard & Phillipson 2010). Thanks to Antiquity, the paper was widely publicised, and Prof. Chris Stringer's contribution to the BBC press release once again highlighted one of the most pressing questions regarding human behavioural and cognitive evolution during the mid-late Upper Pleistocene (here used informally to demarcate the period between roughly 80 000 and 40 000 years ago). He saw the evidence for early bow and arrow technology as adding to the view that modern humans in Africa began to hunt in a new way by 64 000 years ago, and that it further extends the advanced behaviours inferred for early modern people of the continent. According to Stringer, the long gaps in the subsequent record of complex technologies such as the bow and arrow, however, remain perplexing (also see Villa et al. 2010: 640). It may mean that regular use of these weapons did not come until much later, and that the concept of bows and arrows may have been reinvented many millennia afterwards (Stringer pers. comm.).

Similar concerns have been raised by others, not only regarding mechanically projected weaponry, but also about behavioural and cognitive complexity in general. Consensus about whether cultural modernity originated in Africa, or had its roots in multiple continents still has to be reached (e.g. Conard 2010). Many researchers, nonetheless, now accept that human behaviour, associated with the Still Bay and Howiesons Poort stone tool industries between about 75 000 and 60 000 years ago in southern Africa (see Jacobs & Roberts 2008 for discussion on dating), was essentially 'modern', or cognitively and behaviourally complex (Lombard & Parsons 2010). We use 'modern' with caution mostly because it reflects original texts, and we cannot hope to translate the meaning accurately on behalf of others within the framework of current debate (see Shea 2011). In the context of our own discussion, we follow Hovers and Belfer-Cohen's (2006: 296) use of the term as: "relating to, or characteristic of, the present or the immediate past, with no a priori evolutionary connotations. According to this definition, modern behaviour is not necessarily unique to the present, and its presence in the past does not distract from its modernity".

Based on stone tool technology alone, the Still Bay and Howiesons Poort industries show remarkable sophistication, of a kind mostly associated previously with the Upper Palaeolithic in Eurasia, or the Later Stone Age in sub-Saharan Africa--roughly beginning between 50 000 and 40 000 years ago. Yet, stone tool assemblages immediately post-dating the Howiesons Poort (post-Howiesons Poort), between about 58 000 and 50 000 years ago, have been described as "reverting to type" (Deacon 1989: 560), "less sophisticated" (Jacobs & Roberts 2009: 191), and "returning to earlier technological strategies" (McCall 2007: 1749), reminiscent of assemblages pre-dating 75 000 years ago. This perception is predominantly based on early observations regarding the stone tool assemblage from a single site, Klasies River (Singer & Wymer 1982), and the seeming lack of unambiguous symbolic objects during the 10-20 millennia following the Howiesons Poort (see Mitchell 2008 for discussion). Potentially far-reaching explanations of significant episodes of simplification or devolution (Mellars 2007: 7), technological and/or behavioural reversal (McCall 2007: 1749), a material culture cul-de-sac (Henshilwood 2007: 130) or cultural regression (Henshilwood 2005: 455) have been proffered. These interpretations could contribute to views that people living in southern Africa were not behaviourally or cognitively 'fully modern' before about 50 000 years ago (Ambrose & Lorenz 1990; Klein 2001), or that the transition to 'modern human technology' was marked by the change from the Middle Stone Age to the Later Stone Age (e.g. Ambrose 1998a; also see Shea 2011: 12-13).

The notion of technological, behavioural and cognitive regression immediately after the Howiesons Poort may, however, be wide of the mark. We have argued elsewhere (Lombard & Parsons 2010), that previous ideas of similarities between pre-Still Bay and post-Howiesons Poort stone tool assemblages may have been oversimplified and overstated in the literature. We have also suggested continuation in technological behaviour, and levels of cognitive complexity during the post-Howiesons Poort that was not much different from those of recent hunter-gatherers. This argument was based on archaeological evidence of behaviours and traditions that transcend stone tool industries such as hunting behaviour (Lombard 2007a; Clark & Plug 2008; Lombard & Clark 2008), the manufacture of composite tool kits (Lombard 2007b, 2008a; Wadley et al. 2009; Wadley 2010), the technical application of fire (Brown et al. 2009; Wadley in press), the deliberate placement of bedding and hearths (Goldberg et al. 2009), and a prolonged tradition of engraving (Henshilwood et al. 2009; Texier et al. 2010). Here we continue the discussion by exploring issues of reinvention and behavioural or cognitive regression in human evolution by using the bow and arrow as token technology. The paper does not aim to provide any conclusive answers or explanations. Instead (encouraged by Antiquity's editor) it is philosophically speculative and playful, aiming to stimulate discourse.

The rugged landscape of human evolution

Across sub-Saharan Africa, and indeed the entire Old World, mid-late Upper Pleistocene directions of technological change vary from region to region, and even from site to site (Kuhn 2006). These disparities in local technological change probably represent a trend towards regional differentiation. It is likely that regional demarcations materialised in response to specific ecological conditions, demographic and social adjustments, raw material constraints, technological knowledge bases, limits on energy, and time-budgeting factors (Kuhn 2006; Shea & Sisk 2010). Transitions reflected in stone tool assemblages during the mid-late Upper Pleistocene (e.g. from the Middle to Later Stone Age or from the Middle to Upper Palaeolithic) do not represent shifts from one stable condition to another. Phases are dynamic and variable, expressed in different behaviours and on different spatio- temporal scales (Kuhn 2006). It should therefore come as no surprise that we see different kinds of trends over time and space, depending on prevailing variables. To further complicate matters, Middle Stone Age archaeological nomenclature and periodic divisions are often arbitrary and sometimes inaccurately applied, bearing little relation to past realities (Lombard 2008b).

The fact that not all innovative technological trends, such as the bow and arrow, necessarily continued seamlessly from the Middle Stone Age into the Later Stone age, may seem difficult to reconcile with common perceptions of the long-term evolution of Stone Age cultures. Cultural evolution is frequently understood as 'accretive and progressive' (Kuhn 2006:117). Earlier technological systems--for example hand-delivered weaponry such as single component or composite spears--are often seen as incomplete or impoverished versions of later more complex systems such as the bow and arrow. According to this view, human cultural development occurred along a single trajectory, marked by major innovations or advances, and measured in terms of its distance from what is perceived to be modern human behaviour. This unilinear stance derives from early culture evolutionist discourse, and deviates from contemporary notions of evolution as a historically contingent process, based on random production and subsequent reduction of novelty (Kuhn 2006: 117). It also fails to explain the archaeological record.

In order to illustrate how the use of seemingly sophisticated technologies, such as the bow and arrow, may be developed and abandoned by societies through time and space, we draw on the work of Steven Kuhn (2006: 109-120). He applied Sewall Wright's (1932) concept of rugged fitness landscapes to explain trajectories of technological change in the Middle Palaeolithic of Italy. Kuhn's eloquent use of landscape as analogy for understanding variation in fitness solutions and evolutionary paths is particularly appealing. He suggests that a rugged fitness landscape model is an effective concept to help explain what we observe archaeologically. A fitness landscape is a theoretical construct that reflects the influence of different factors on the fitness of a population. Higher points in this topographic landscape represent adaptive configurations of greater fitness than lower points. In a simple landscape, all factors converge to create a single high peak--a single behavioural or physical phenotype that provides a most favourable adaptive solution to a wide range of problems. In the simple fitness landscape scenario, selection will tend to drive populations toward this single peak from anywhere in the landscape. On the other hand, rugged fitness landscapes consist of many peaks of varying heights. The valleys separating peaks represent lower fitness adaptations (Kuhn 2006).

In a complex topographic landscape, populations will tend to climb the peaks closest to their starting point (which may or may not be the highest peak in the landscape). Theory dictates that once a population has started their ascent of a particular fitness peak, it is difficult to shift to another. Even moving to a peak that may provide greater fitness could be challenging as shifting between peaks would first involve a reduction in fitness--something that is rarely promoted by evolutionary processes. According to Kuhn (2006), severe environmental or demographic change may, however, dislodge a population from its existing summit allowing it to access another, possibly even higher peak. In addition to climate and demography, we suggest that such fitness displacements may also occur as a result of dramatic shifts or disruptions in the socio-cultural and/or ideological organisation of a society.

Viewed within this theoretical framework, it is conceivable that developing and using bow and arrow technology during the Howiesons Poort could have been one of many elements within a specific evolutionary trajectory. Any, or a combination of many, variable(s) could have forced or encouraged a shift in behaviour and technology to a different fitness solution. Such a shift would have required reduction in a population's existing fitness repertoire in order to deal with challenges and regain momentum for attaining new fitness levels. At different points on the topography of human evolution, bow and arrow hunting may thus have been an element that sometimes became redundant, depending on the technological and behavioural evolutionary trajectory of any specific society.

The fickleness of the archaeological record and human memory

Erella Hovers and Anna Belfer-Cohen (2006: 295-304) provide a complementary explanation for the seemingly erratic occurrence of traits frequently linked with so-called modern behaviour during the mid-late Upper Pleistocene. We are reminded that: "archaeological finds reflect only those elements of human knowledge that have been accepted and incorporated into societal normative behaviours, stored and kept for repeated use through canonisation and rituals" (Hovers & Belfer-Cohen 2006: 295). They suggest that unstable demographic systems interrupted the build-up of such knowledge in certain regions, leading to repeated reinvention of technological and symbolic innovations. In addition, it is pointed out that it has long been assumed that the archaeological record would unmistakeably attest to the potential for modern cognitive behaviour. This view proved to be overly simplistic. As anthropological thought develops, archaeological theory increasingly accepts that the material record provides only limited glimpses of past human cognition. In addition, our datasets can accommodate multiple valid, yet sometimes contradictory interpretations, whilst seldom providing direct answers (e.g. Hovers & Belfer- Cohen 2006).

In order to meet these challenges, and help interpret the archaeological record, Hovers and Belfer-Cohen (2006) suggest drawing on biology. By using the terms 'phenotypic' (for the realisation or actualisation of certain types of behaviour), and 'genotypic' (for the latent capacity for such behaviours) we are able to gain some insight. As with biological phenotypes, some behaviours will only become apparent in response to particular stimuli.

The first recognisable appearance of behaviour, consequently, does not necessarily indicate that its cognitive potential had only just emerged. Because stimuli are circumstance-dependent, distinct populations with similar cognitive abilities may also exhibit different behaviours (Hovers & Belfer-Cohen 2006). Inventions such as the bow and arrow become fully developed innovations, integrated within an observable behavioural repertoire, only when widely adopted. In the process, knowledge (which encompasses past experience and the inclination to experiment) acts as a pre-adaptive matrix within which new ideas are tested and practiced. The adoption of inventions relate to a range of social, technical and psychological circumstances, whilst the spread of knowledge that support the use of such technologies depends on social, physical and organisational infrastructure (de Beaune 2004; Hovers & Belfer-Cohen 2006).

A new behaviour, such as the use of mechanically projected weaponry, that is archaeologically observable, implies that complex processes of diffusion and adoption had turned an invention into an innovation. For such behaviour to persist, the pertinent knowledge must be retained by passing it on from one generation to the next. As a rule, cultural information (i.e. sets of beliefs, ideas and practices that allow individual identification with a broader community) has to be remembered and transmitted again and again with little or no alteration, or else the accumulation of alteration will compromise the very existence of the culture (Hovers & Belfer-Cohen 2006; Wurz 2008). In this sense, tradition needs to be accepted unquestioningly and dissent cannot be afforded. In nonliterate societies, information is retained through oral tradition and cultural transmission. Information needed for mediating mundane needs and frequently recurrent stress events is in constant use, and therefore easily accessible. In contrast, however, information for dealing with rare crises has a higher risk of being lost (Hovers & Belfer-Cohen 2006).

Rites and rituals canonise knowledge as part of a group's cultural heritage and identity (Hovers & Belfer-Cohen 2006). Thus changes in ritual could be risky in terms of ecological balance and the social unity of a group. In the absence of networks of storage and transmission of knowledge, innovative behaviour is essential to the group's survival. Hovers and Belfer-Cohen (2006) suggest a close link between mundane and ritual domains and note that the social retention of some mundane behaviour may be dependent on the existence of ritual ideology. Thus, the intermittent occurrence of some behaviours, such as complex technologies, may reflect cases where systems of knowledge retention became unstable. Once again it is illustrated that the spread and persistence of behavioural and cognitive complexity is a function of historical contingency, rather than progressive culture change.

Does technological simplification equal behavioural regression or non-modernity?

We used the theoretical frameworks above as examples that can explain the idiosyncratic mid-late Upper Pleistocene archaeological record. Thus, we argue that it is not feasible to take for granted that once societies adopt useful technologies, such as mechanically projected weapon systems, they inevitably retain them until a better solution is found. Technological innovations must not only be acquired, they also have to be maintained across generations. Long-term maintenance, similar to invention, depends on many unpredictable factors. Apart from the physical environment, all societies go through social trends and changes in ideology. Sometimes such trends cause useless objects to become 'valued' or useful things to be provisionally 'devalued'. A society that in the interim turned against powerful technology would possibly continue to observe its use by neighbouring societies. They would, therefore, have the opportunity to re-acquire it by diffusion. If they fail to do so, or unless they become geographically or socially isolated, they will most likely be absorbed or conquered by their technologically empowered neighbours (Diamond 2005).

These theoretical frameworks help to explain technological simplification and reinvention observed in the archaeological record through time and space. Yet, they are not only relevant to the deep past. Jared Diamond's (2005) synthesis shows that it is also true for current modern societies for which he provides ample historical and ethnographical cases in point (for theoretical and analytical research also see Shennan 2001; Henrich 2004; Powell et al. 2009). For instance, after AD 1600, Japan abandoned gun production for socio/ideological reasons until it was almost void of functional firearms. Its safety in isolation came to an end in 1853 when an American fleet, laden with canons, visited the island and convinced Japan of its need to resume gun manufacture. China, for a while, abandoned ocean-going ships, mechanical clocks and water-driven spinning machines. Torres Islanders abandoned canoes, while Gaua Islanders abandoned and then readopted them. Pottery was abandoned throughout Polynesia. The boomerang was abandoned in the Cape York Peninsula of north-eastern Australia. The Moriori, descendents of Polynesian farmers, split from the Maori settlers of New Zealand to colonise the Chatham Islands. As opposed to the Maori, Moriori political organisation and technology became less complex, and they reverted to being hunter-gatherers. The most extreme case of technological simplification is probably that of the Tasmanians, who abandoned even bone tools and fishing to become the society with the simplest technology in the modern world (Diamond 2005; also see Henrich 2004).

If it is indeed the case that people in southern Africa used bows and arrows by 64 000 years ago, and stopped doing so after about 59 000 years ago (the latter is not a foregone conclusion though), it is not the first or only time this happened. Even though mechanically projected weaponry is a crucial component of all recent human subsistence strategies (Shea 2009), its use was by no means continuous in all societies. Throughout human history it has been adopted, discarded and adopted again. Relatively recent (Holocene) examples would include Polynesians and Metanesians who abandoned the use of bows and arrows in war, Polar and Dorset Eskimos who 'lost' the bow and arrow, and Aboriginal Australians, who may have adopted and abandoned bows and arrows (Diamond 2005; but see Attenbrow et al. 2009 regarding Australia). Felix Riede (2008) presented archaeological evidence for the demise of bow and arrow technology in a European context. According to him, the large eruption of the Laacher See volcano at about 15 000 years ago in present-day western Germany, had a dramatic impact on forager demography. It triggered archaeologically visible cultural change along the northern periphery of Late Glacial European settlement. In southern Scandinavia, these changes took the form of technological simplification--including the loss of bow and arrow technology.

Taking an exploratory and slightly broader view of our ancestors' fluctuating dependence on bow and arrow technology has wider application for how we view behavioural evolution. For example, other recent technologies that are, in some contexts, conspicuously missing from the archaeological and historical records, despite the easy assumption that they were integral to the story of human development, include the use of the wheel, metalworking, and a commitment to food production. These practices clearly imply considerable cognitive and behavioural sophistication, but it would be highly unusual to interpret their absence as a decrease in, or lack of, complex behaviour and cognition. Based on its current and recent manifestation, we argue that technological simplification cannot be interpreted as behavioural regression or devolution. The cognitive and behavioural complexity of Holocene societies who chose, or were forced to adopt, simpler technologies, for whatever reason(s), cannot be questioned. It therefore follows that technological simplification, and the possible loss of bow and arrow technology after about 59 000 years ago is not a convincing indicator that people were not 'fully modern' during the mid-late Upper Pleistocene in southern Africa or, for that matter, elsewhere in the Old World.

Back to the post-Howiesons Poort

Thus far several hypotheses have been advanced to explain the transition flora the Howiesons Poort to the post-Howiesons Poort. Most prevalent is the notion of dramatic climatic changes that influenced demographic dynamics so negatively that the archaeological signature becomes almost invisible during the post-Howiesons Poort (e.g. Ambrose 2002; Klein et al. 2004; Klein 2009). Yet, Peter Mitchell's (2008) discussion of southern African sites occupied during Marine Isotope Stage 3 suggests the opposite (also see Villa et al. 2010). He re-introduced as many sites with post-Howiesons Poort occupation across southern Africa as those with the Howiesons Poort. Thus, based on site representation alone, it can no longer be argued that the southern African landscape was largely depopulated after about 60 000 years ago.

One explanation that could correlate with most of the archaeological data and the theoretical models presented in this paper, hinges on changes in diversification and intensification (e.g. Deacon 1989; Henshilwood & Marean 2003; Clark & Plug 2008; Lombard 2009; Shea 2009). Shea (2009) suggested that diversification and intensification were likely to increase after about 75 000 years ago in Africa. The accumulation of polar ice could have dried out parts of the continent; drill cores from three lakes in East and West Africa indicate periods of extreme aridity in tropical Africa between about 135 000 and 75 000 years ago (Scholtz et al. 2007). These conditions probably resulted in numerous demographic 'bottlenecks', consequently dropping the number of reproducing populations (Shea 2009), but not necessarily the number of people. This hypothesis is furthermore inferred from genetic variation amongst living humans supporting a scenario in which populations were packed into African equatorial woodland refugia (also see Ambrose 1998b), and an episode of rapid population growth in ancestral African populations around this time (Mellars 2006). We suggest that pockets within the southern African region probably also served as refugia between about 75 000 and 60 000 years ago. This would explain the behavioural and technological florescence we see represented in the archaeological record around the coast, and at some inland sites on the subcontinent during this phase.

Concentration of Homo sapiens populations within refugia may have provided strong incentives for increasing the effectiveness and versatility of behaviours and technologies, including the adoption of bow and arrow technology (e.g. Shea 2009), and the spread of inventions from group to group. Subsequent amelioration of conditions surrounding refugia would have opened up the landscape, providing opportunities for innovations and populations to expand across the continent and northwards. On the flip side, the subsequent drop in population densities also could have caused the isolation of groups, and have led to the loss of, or simplified technology (e.g. Henrich 2004). This scenario would be consistent with Kuhn's rugged fitness landscape where different societies were climbing different peaks, and where changes in the fitness landscape can encourage or force them to shift between fitness peaks--sometimes undergoing technological change and/or simplification. The truth is, however, that we still know too little about climatic change in the different ecological zones of the region, population sizes, and gene flows or drifts, to realistically reconstruct the dynamics of the Howiesons Poort/post-Howiesons Poort transition (Mellars 2006; Jacobs et al. 2008). Thus, explanations for technological change based on climate and demography remain hypothetical--for the time being.

If we follow the suggestion that bow and arrow technology is understood as a niche-broadening technology, rather than as just a means for killing large game (Shea 2009), it is plausible that its discontinuation under certain circumstances may reflect a group's increased specialisation in hunting specific species with more specialised weaponry such as traps, snares or spears. What is more, and perhaps somewhat contentiously, we want to argue that it is premature to conclude that the post-Howiesons Poort was a period of technological simplification. For various reasons, we do not yet have a comprehensive understanding of the lithic assemblages represented between about 60 000 and 40 000 years ago in southern Africa (e.g. Mitchell 2008; Villa et al. 2010). When behaviours and technologies that transcend stone tool production are considered, a different story seems to be emerging (Lombard & Parsons 2010).

Concluding remarks

Drawing on past and current theorising, and focusing on a single technological innovation, this paper explored alternative ways of thinking about the human mind after the Howiesons Poort. The apparent disappearance of the bow and arrow was used as proxy for other changes; changes sometimes interpreted to signal the lack of 'fully modern' human behaviour, or as behavioural and cultural regression or devolution. It is becoming clear, however, that our ancestors did not evolve in a unilinear fashion--that, in Kuhn's terms, their fitness landscape was rugged rather than simple--and that the complicated processes of maintaining innovations are ultimately, historically contingent. If we accept this, notions of human behavioural regression to explain change in the mid-late Upper Pleistocene archaeological record of southern Africa risk glossing over a chapter in the human story. This chapter may disclose that, although clearly different from the preceding phase, human behaviour and cognition between about 60 000 and 40 000 years ago in the region was not necessarily less complex.

Acknowledgements

We thank those who inspired this paper, either by their work or their encouragement. Opinions and mistakes remain our own.

References

AMBROSE, S.H. 1998a. Chronology of the Later Stone Age and food production in East Africa. Journal of Archaeological Science 25: 377-92.

--1998b. Late Heistocene human population bottlenecks, volcanic winter, and differentiation of modern humans. Journal of Human Evolution 34: 623-51.

--2002. Small things remembered: origins of early microlithic industries in sub-Saharan Africa, in S. Kuhn & R. Elston (ed.) Thinking small: global perspectives on microlithization (Anthropological Papers of the American Anthropological Association 12): 9-29. Arlington (VA): American Anthropological Association.

AMBROSE, S.H. & K.G. LORENZ. 1990. Social and ecological models for the Middle Stone Age in southern Africa, in P. Mellars (ed.) The emergence of modern humans: 3-33. Edinburgh: Edinburgh University Press.

ATTENBROW, V., G. ROBERTSON & P. HISCOCK. 2009. The changing abundance of backed artefacts in south-eastern Australia: a response to Holocene climate change? Journal of Archaeological Science 36: 2765-70.

DE BEAUNE, S.A. 2004. The invention of technology. Current Anthropology 45: 139-62.

BROWN, K., C.W. MAREAN, A.I.R. HERRIES, Z. JACOBS, C. TRIBOLO, D. BRAUN, D.L. ROBERTS, M.C. MEYER & J. BERNATCHEZ. 2009. Fire as an engineering tool of early modern humans. Science 325: 859-62.

CLARK, J.L. & I. PLUG. 2008. Animal exploitation strategies during the South African Middle Stone Age: Howiesons Poort and post-Howiesons Poort fauna from Sibudu Cave. Journal of Human Evolution 54: 886-98.

CONARD, N.J. 2010. Cultural modernity: consensus or conundrum? Proceedings of the National Academy of Sciences 107: 7621-2.

DEACON, H.J. 1989. Late Pleistocene palaeoecology and archaeology in the southern Cape, South Africa, in P. Mellars & C. Stringer (ed.) The human revolution: behavioural and biological perspectives on the origins of modern humans: 547-64. Edinburgh: Edinburgh University Press.

DIAMOND, J. 2005. Guns, germs and steel: a short history of everybody for the last 13,000 years. London: Vintage Books.

GOLDBERG, P., C.E. MILLER, S. SCHIEGL, B. LIGOUIS, F. BERNA, N.J. CONARD & L. WADLEY. 2009. Bedding, hearths and site maintenance in the Middle Stone Age of Sibudu Cave, KwaZulu-Natal, South Africa. Archaeological and Anthropological Science 1: 95-122.

HENRICH, J. 2004. Archaeology, demography and cultural evolution: how adaptive cultural processes can produce maladaptive losses--the Tasmanian case. American Antiquity 69: 197-214.

HENSHILWOOD, C.S. 2005. Stratigraphic integrity of the Middle Stone Age levels at Blombos Cave, in F. d'Errico & L. Backwell (ed.) From tools to symbols: from early hominids to modern humans: 441-58. Johannesburg: Witwatersrand University Press.

--2007. Fully symbolic sapiens behaviour: innovations in the Middle Stone Age at Blombos Cave, South Africa, in P. Mellars, K. Boyle, O. Bar-Yosef & C. Stringer (ed.) Rethinking the human revolution: new behavioural and biological perspectives on the origin and dispersal of modern humans: 123-32. Cambridge: McDonald Institute.

HENSHILWOOD, C.S. & C.W. MAREAN. 2003. The origin of modern human behaviour: a critique of the models and their test implications. Current Anthropology 44: 627-51.

HENSHILWOOD, C.S., F. D'ERRICO & I. WATTS. 2009. Engraved ochres from the Middle Stone Age levels at Blombos Cave, South Africa. Journal of Human Evolution 57: 27-47.

HOVERS, E. & A. BELFER-COHEN. 2006. 'Now you see it, now you don't': modern human behaviour in the Middle Paleolithic, in E. Hovers & S.L. Kuhn (ed.) Transitions before the transition: evolution and stability in the Middle Paleolithic and Middle Stone Age: 295-304. New York: Springer.

JACOBS, Z. & R.G. ROBERTS. 2008. Testing times: old and new chronologies for the Howiesons Poort and Still Bay industries in environmental context. South African Archaeological Society Goodwin Series 10: 9-34.

--2009. Catalysts for Stone Age innovations: what might have triggered two short-lived bursts of technological and behavioral innovation in southern Africa during the Middle Stone Age? Communicative & Integrative Biology 2: 191-3.

JACOBS, Z., R.G. ROBERTS, R.E GALBRAITH, H.J. DEACON, R. GRUN, A. MACKAY, P. MITCHELL, R. VOGELSANG & L. WADLEY. 2008. Ages for the Middle Stone Age of southern Africa: implications for human behavior and dispersal. Science 322: 733-5.

KLEIN, R.G. 2001. Southern Africa and modern human origins. Journal of Anthropological Research 57: 1-16.

--2009. The human career: human biological and cultural origins. Chicago: University of Chicago Press.

KLEIN, R.G., G. AVERY, K. CRUZ-URIBE, D. HALKETT, J.E. PARKINGTON, T. STEELE, T.P. VOLMAN & R. YATES. 2004. The Ysterfontein 1 Middle Stone Age site, South Africa, and early human exploitation of coastal resources. Proceedings of the National Academy of Sciences 101: 5708-715.

KUHN, S.L. 2006. Trajectories of change in the Middle Paleolithic in Italy, in E. Hovers & S.L. Kuhn (ed.) Transitions before the transition: evolution and stability in the Middle Paleolithic and Middle Stone Age: 109-120. New York: Springer.

LOMBARD, M. 2007a. Evidence for change in Middle Stone Age hunting behaviour at Blombos Cave: results of a macrofracture analysis. South African Archaealogical Bulletin 62: 62-7.

--2007b. The gripping nature of ochre: the association of ochre with Howiesons Poort adhesives and Later Stone Age mastics from South Africa. Journal of Human Evolution 53: 406-419.

--2008a. Finding resolution for the Howiesons Poort through the microscope: micro-residue analysis of segments from Sibudu Cave, South Africa. Journal of Archaeological Science 35: 26-41.

--2008b. From testing rimes to high resolution: the late Pleistocene Middle Stone Age of South Africa and beyond. South African Archaeological Society Goodwin Series 10: 180-88.

--2009. The Howieson's Poort of South Africa amplified. South African Archaeological Bulletin 189: 4-12.

LOMBARD, M. & J.L. CLARK. 2008. Variability and change in Middle Stone Age hunting behaviour: aspects from the lithic and faunal records, in S. Badenhorst, P. Mitchell & J.C. Driver (ed.) People, places and animals of Africa: essays in honour of Ina Plug: 46-56 (British Archaeological Reports international series 1849). Oxford: Archaeopress.

LOMBARD, M. & I. PARSONS. 2010. Factor fiction? Behavioural and technological reversal after 60 ka in southern Africa. South African Archaeological Bulletin 65: 224-8.

LOMBARD, M. & L. PHILLIPSON. 2010. Indications of bow and stone-tipped arrow use 64 000 years ago in KwaZulu-Natal, South Africa. Antiquity 84: 635-48.

MCCALL, G.S. 2007. Behavioral ecological models of lithic technological change during the later Middle Stone Age of South Africa. Journal of Archaeological Science 34: 1738-51.

MELLARS, P. 2006. Why did modern human populations disperse from Africa ca. 60,000 years ago? Proceedings of the National Academy of Science 103: 9381-6.

--2007. Rethinking the human revolution: Eurasian and African perspectives, in P. Mellars, K. Boyle, O. Bar-Yosef & C. Stringer (ed.) Rethinking the human revolution: new behavioural and biological perspectives on the origin and dispersal of modern humans: 1-14. Cambridge: McDonald Institute.

MITCHELL, P. 2008. Developing the archaeology of Marine Isotope Stage 3. South African Archaeological Society Goodwin Series 10: 52-65.

POWELL, A., S. SHENNAN & M.G. THOMAS. 2009. Late Pleistocene demography and the appearance of modern human behavior. Science 324: 1298-1301.

RIEDE, F. 2008. The Laacher See-eruption (12,920 BP) and material culture change at the end of the Allerod in northern Europe. Journal of Archaeological Science 35: 591-9.

SCHOLTZ, C.A., T.C. JOHNSON, A.S. COHEN, J.W. KING, J.A. PECK, J.T. OVERPECK, M.R. TALBOT, E.T. BROWN, L. KALINDEKAFE, P.Y.O. AMOAKO, R.P. LYONS, T.M. SHANAHAN, I.S. CASTAEDA, C.W. HEIL, S.L. FORMAN, L.R. MCHARGUE, K.R. BEUNING, J. GOMEZ & J. PEISON. 2007. East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins. Proceedings of the National Academy of Sciences 104: 16416-21.

SHEA, J.J. 2009. The impact of projectile weaponry on Late Pleistocene hominin evolution, in J. Hublin & M.P. Richards (ed.) The evolution of hominin diets: integrating approaches to the study of Paleolithic subsistence. Dordrecht: Springer.

--2011. Homo sapiens is as Homo sapiens was: behavioural variability versus 'behavioural modernity' in Paleolithic archaeology. Current Anthropology 52: 1-35.

SHEA, J.J. & M.L. SISK. 2010. Complex projectile technology and Homo sapiens dispersal into western Eurasia. PaleoAnthropology 2010: 100-122.

SHENNAN, S. 2001. Demography and cultural innovation: a model and its implications for the emergence of modern human culture. Cambridge Archaeological Journal 11: 5-16.

SINGER, R. & J. WYMER. 1982. The Middle Stone Age at Klasies River Mouth in South Africa. Chicago (IL): University of Chicago Press.

TEXIER, P-J., G. PORRAZ, J. PARKINGTON, J-P. RIGAUD, C. POGGENPOEL, C. MILLER, C. TRIBOLO, C. CARTWRIGHT, A. COUDENNEAU, R. KLEIN, T. STEELE & C. VERNAI. 2010. A Howiesons Poort tradition of engraving ostrich eggshell containers dated to 60,000 years ago at Diepkloof Rock Shelter, South Africa. Proceedings of the National Academy of Science 107: 6180-85.

VILLA, P., S. SORIANO, N. TEYSSANDIER & W. WURZ. 2010. The Howiesons Poort and MSA III at Klasies River main site, Cave 1A. Journal of Archaeological Science 37: 630-55.

WADLEY, L. 2010. Compound-adhesive manufacture as a behavioral proxy for complex cognition in the Middle Stone. Current Anthropology 51 (Supplement 1): S111-S119.

--In press. Some combustion features at Sibudu, South Africa, between 65,000 and 58,000 years ago. Quaternary International doi: 10.1016/j.quaint.2010.10.026.

WADLEY, L., T. HODGSKISS & M. GRANT. 2009. Implications for complex cognition from the hafting of tools with compound adhesives in the Middle Stone Age, South Africa. Proceedings of the National Academy of Sciences 106: 9590-94.

WRIGHT, S. 1932. The roles of mutation, inbreeding, crossbreeding and selection in evolution. Proceedings of the Sixth International Congress on Genetics 1: 356-66.

WURZ, S. 2008. Modern behaviour at Klasies River. South African Archaeological Society Goodwin Series 10: 150-56.

Marlize Lombard (1) & Isabelle Parsons (2)

(1) Department of Anthropology and Development Studies, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa (Email: mlombard@uj.ac.za)

(2) Department of Anthropology & Archaeology, University of South Africa, P.O. Box 329, UNISA 0003, South Africa